1. Field
The following description relates to an in-wheel actuator applicable to a vehicle, such as an electric automobile, which is driven with electrical power, and an in-wheel assembly comprising the same.
2. Description of the Related Art
Hybrid vehicles and electric vehicles have gained more popularity due to harmful environmental effects from air pollution and shortage of fossil fuels. A hybrid vehicle mainly uses an internal-combustion engine to generate power and uses an electric motor as an auxiliary power source. An electric vehicle uses an electric motor as a main power source.
With the development of technologies for batteries and motors, it is expected that electric vehicles, known as pollution-free vehicles, replace “transition” vehicles, such as hybrid vehicles, since electric vehicles emit no pollutants or carbon dioxide during driving.
An in-wheel system has a driving motor mounted in a wheel, transfers power from the driving motor directly to the wheel. The application of the in-wheel system allows a vehicle to have a compact and organized driving system, thereby reducing vehicle weight and improving a degree of freedom in vehicle layout or design. In addition, the in-wheel system contributes to optimization of a vehicle frame to increase collision safety. Further, the in-wheel system increases drive motor performance of the vehicle and facilitates a larger interior space by optimally balancing the weight across the vehicle.
A break and a bearing, supporting a hub, are installed inside a wheel of the above-mentioned in-wheel assembly. Further, a driving motor is installed in the rest of the inside of the wheel. Therefore, to prevent an interruption from a vehicle body, a slim driving motor is required. However, there is a limit to reducing the size of the driving motor, since a high output torque is needed for driving a vehicle. In order to generate high output torque and reduce the size of a driving motor, a decelerator may be installed in an output shaft of a driving motor so as to increase output torque, so that both the decelerator and the driving motor are installed inside of the wheel.
When operation of the driving motor and the decelerator occurs, both the driving motor and the decelerator are heated. Therefore, if the heat of the driving motor is transferred to the decelerator, the temperature of the decelerator may exceed a limited operating temperature. Further, if the heat of the decelerator is transferred to the driving motor, the temperature of the driving motor may increase. Thus, endurance and performance of the driving motor may be affected. Therefore, there is a need for a technology to efficiently cool down a decelerator.